Microtunneling method

ABSTRACT

A microtunneling method includes: (a) forming a working well; (b) boring a tunnel from the working well through waterjet techniques which use at least one waterjet cutter including a jet seat and a jet nozzle mounted rotatably on the jet seat, the tunnel being bored by moving progressively the jet seat along a circular path and by rotating the jet nozzle relative to the jet seat; (c) removing excavated soil, rocks or gravel from the tunnel; and (d) advancing the waterjet cutter along an axis of the circular path.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a microtunneling method, more particularly to a microtunneling method using waterjets techniques.

2. Description of the Related Art

Conventional contact-type tunnel boring machines normally have disadvantages, such as the inability of providing sufficient friction and abutment force during cutting a hard rock structure or the problem of undesired attachment of cement onto the cutting head during cutting a cement structure, which results in a decrease in cutting efficiency. As a consequence, there is normally required additional manpower to bore the tunnel and to remove the attached cement on the cutting head. In microtunneling (tunnel diameter less than 900 mm), particularly, for tunnel diameter less than 600 mm, the aforesaid drawbacks become more severely, and result in an increase in the operation cost, a decrease in boring efficiency, dust and noise pollution problems, safety concerns, insufficient emergent response space, etc.

FIG. 1 illustrates a conventional semi-contact type tunnel boring machine that includes a tubular tunnel support 10, a front end plate 11, a disc cutter 12 mounted rotatably on the front end plate 11 and provided with a drilling head 121, a motor 13 for driving rotation of the disc cutter 12, a screw rod conveyor 14 for removing excavated soil, rocks or gravel from a collecting chamber 15, a first waterjet unit 16 having a plurality of first jet nozzles 161 mounted on the front end plate 11, and a second waterjet unit 17 having a plurality of second jet nozzles 171 mounted on the drilling head 121. When working on a hard working surface of a cement structure (not shown), such as a gravel layer structure or a grouted soil, rocks or gravel structure, in a working well (not shown) to bore a tunnel into the ground, the first and second waterjet units 16, 17 are actuated to provide water jets through the first and second jet nozzles 161, 171 so as to pre-weaken the structure of the hard working surface of the cement structure. Note that the water jet can be plain water jet or abrasive water jet. The disc cutter 12 is then actuated by the motor 13 to rotate in order to cut through the weakened hard working surface, and to move the excavated soil, rocks or gravel into the collecting chamber 15. The screw rod conveyor 14 extends into a bottom of the collecting chamber 15 so as to remove the excavated soil, rocks or gravel therefrom.

Although the structure of the hard working surface of the cement structure can be pre-weakened before the actual cutting operation, only a limited area of the hard working surface covered by the first and second jet nozzles 161, 171 is pre-weakened, and the structure of the remainder area of the hard working surface remains relatively strong. Hence, the effect of facilitating the subsequent cutting operation through pre-weakening of the structure of the hard working surface using the first and second waterjet units 16, 17 is limited.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a microtunneling method that can overcome the aforesaid drawback associated with the prior art.

According to this invention, there is provided a microtunneling method that comprises: (a) forming a working well; (b) boring a tunnel from the working well through waterjet techniques which use at least one waterjet cutter including a jet seat and a jet nozzle mounted rotatably on the jet seat, the tunnel being bored by moving progressively the jet seat along a circular path and by rotating the jet nozzle relative to the jet seat; (c) removing excavated soil, rocks or gravel from the tunnel; and (d) advancing the waterjet cutter along an axis of the circular path.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a conventional tunnel boring machine;

FIG. 2 is a flow chart illustrating consecutive steps of the first preferred embodiment of a microtunneling method according to this invention;

FIG. 3 is a fragmentary schematic view to illustrate a state where a working well is formed according to the first preferred embodiment and where a tunnel boring machine is installed in the working well;

FIG. 4 is a fragmentary schematic view to illustrate another state where a tunnel is bored using the tunnel boring machine according to the first preferred embodiment;

FIG. 5 is a schematic view to illustrate the configuration of a waterjet cutter of the tunnel boring machine used in the first preferred embodiment;

FIG. 6 is a schematic view illustrating a boring pattern on a working surface of the tunnel bored by the waterjet cutter used in the first preferred embodiment;

FIG. 7 is a schematic view to illustrate the configuration of a waterjet cutter of the tunnel boring machine used in the second preferred embodiment of the method of this invention;

FIG. 8 is a schematic view illustrating a boring pattern on the working surface of the tunnel bored by the waterjet cutter used in the second preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in greater detail, it should be noted that same reference numerals have been used to denote like elements throughout the specification.

FIG. 2 illustrates consecutive steps of the first preferred embodiment of a microtunneling method according to this invention for boring a tunnel. The method includes the steps of: (a) forming a working well 100 (see FIG. 3); (b) boring a tunnel 200 from the working well 200 (see FIG. 4) through waterjets techniques which use a first waterjet cutter 3 including three first jet seats 332 and three first jet nozzles 331 mounted rotatably on the first jet seats 332, respectively, the tunnel 200 being bored by moving progressively the first jet seats 332 along a first circular path 300 (see FIG. 5) and by rotating the first jet nozzles 331 relative to the respective first jet seats 332; (c) removing excavated soil, rocks or gravel from the tunnel 200; and (d) advancing the first waterjet cutter 3 along an axis of the first circular path 300. A high water pressure generator 30 is connected to the first jet nozzles 331 through a supply line 301 (see FIG. 3) for supplying high pressure water jets through the first jet nozzles 331.

In this embodiment, the first waterjet cutter 3 further includes a first circular rail 31 that defines the first circular path 300. The first nozzle seats 332 are mounted slidably on the first circular rail 31, and are moved progressively and intermittently along the first circular rail 31 during the boring operation. Each of the first nozzle seats 332 is moved a predetermined pace on the circular path 300 each time. Each of the first jet nozzles 331 is then actuated and is rotated 360 degrees relative to the respective first nozzle seat 332 so as to form a circular groove 34 in a working surface 201 of the tunnel 200 each time (see FIG. 6). Hence, by repeating the alternating movements and operations of the first nozzle seats 332 and the first jet nozzles 331, it is possible to bore through the entire working surface 201 of the tunnel 200. It is noted that the predetermined pace each first nozzle seat 332 is advanced on the first circular rail 31 each time is adjusted such that each circular groove 34 thus formed overlaps the adjacent circular grooves 34 (see FIG. 6) to an extent that permits boring of the entire area of the working surface 201 of the tunnel 200.

The first circular rail 31 is received in and is secured to a tubular tunnel support 2 (see FIGS. 3 and 4) through a plurality of abutting springs 32. Each abutting spring 32 abuts against the first circular rail 31 and the tubular tunnel support 2 so as to hold the first circular rail 31 onto the tubular tunnel support 2 and to provide a cushioning effect. Advancement of the tubular tunnel support 2 in the tunnel 200 along the axis is conducted using pipe jacking techniques. When the tubular tunnel support 2 is entirely thrusted into the tunnel 200, an extension support 8 is subsequently inserted into the working well 100 and is connected to a rear open end of the tubular tunnel support 2 (see FIG. 4). The tubular tunnel support 2 and the extension support 8 are thrusted into the tunnel 200 using a hydraulic jack 4 (see FIGS. 3 and 4). The rear open end of the tubular tunnel support 2 is closed by a door 51. The hydraulic jack 4 includes a rear abutment 42 and a plurality of hydraulic cylinders 45 extending from the rear abutment 42 and a butting against the door 51 of the tubular tunnel support 2 (or abutting against a rear open end of the extension support 8 when the tubular tunnel support 2 is entirely received in the tunnel 200) so as to urge a front open end 23 of the tubular tunnel support 2 (see FIG. 3) to abut against the working surface 201 of the tunnel 200. The hydraulic jack 4 further includes a pressure sensor 41 for detecting the pressure of the hydraulic cylinders 45 acting on the tubular tunnel support 2 or the extension support 8, and an alignment control servo mechanism 43 connected to the front open end 23 of the tubular tunnel support 2 and having equiangularly disposed radial hydraulically adjusting elements 431 for keeping alignment of the tubular tunnel support 2 along the axis. An optical positioner 7 is used to assist alignment of the tubular tunnel support 2.

A pumping unit 6 includes a pump 63 connected to a chamber defined by the tubular tunnel support 2 through a mud pipe line 61 and a water pipe line 62 so as to remove the excavated soil, rocks or gravel collected in the chamber of the tubular tunnel support 2.

FIG. 7 illustrates the second preferred embodiment of the microtunneling method according to this invention. The second preferred embodiment differs from the previous embodiment in that in step (b), a second waterjet cutter 9 is further included to bore the tunnel 200. In this embodiment, the second waterjet cutter 9 includes a second circular rail 91 that is disposed coaxially with the first circular rail 31, three second nozzle seats 932 that are mounted slidably on the second circular rail 91, and three second jet nozzles 931 that are mounted rotatably on the second jet seats 932, respectively. Each of the second nozzle seats 932 is moved progressively and intermittently along the second circular rail 91. Each of the second jet nozzles 931 is rotated relative to the respective second nozzle seat 932 during the boring operation. The second circular rail 91 is secured to the tubular tunnel support 2 through a plurality of abutting springs 92.

FIG. 8 illustrates a boring pattern on the working surface 201 of the tunnel 200 bored by the second waterjet cutter 9.

By virtue of the configuration of the first and second waterjet cutters 3, 9 used in the microtunneling method of this invention, the aforesaid drawback associated with the prior art can be eliminated.

While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements. 

1. A microtunneling method comprising: (a) forming a working well; (b) boring a tunnel from the working well through waterjet techniques which use at least one first waterjet cutter including a first jet seat and a first jet nozzle mounted rotatably on the first jet seat, the tunnel being bored by moving progressively the first jet seat along a first circular path and by rotating the first jet nozzle relative to the first jet seat; (c) removing excavated soil, rocks or gravel from the tunnel; and (d) advancing the first waterjet cutter along an axis of the first circular path.
 2. The microtunneling method of claim 1, wherein the first waterjet cutter further includes a first circular rail that defines the first circular path, the first nozzle seat being mounted slidably on the first circular rail, and being moved progressively and intermittently along the first circular rail during the boring operation.
 3. The microtunneling method of claim 2, wherein in step (b), a second waterjet cutter is further included to bore the tunnel, the second waterjet cutter including a second circular rail that is disposed coaxially with the first circular rail, a second nozzle seat that is mounted slidably on the second circular rail, and a second jet nozzle that is mounted rotatably on the second jet seat, the second nozzle seat being moved progressively and intermittently along the second circular rail and the second jet nozzle being rotated relative to the second nozzle seat during the boring operation.
 4. The microtunneling method of claim 2, wherein the first circular rail is received in and is secured to a tubular tunnel support, advancement of the tubular tunnel support in the tunnel along the axis being conducted using pipe jacking techniques. 